Hadron-Quark phase transition in the context of GW190814

TL;DR

This paper investigates the hadron-quark phase transition in neutron stars using advanced models, analyzing how it affects star properties and the interpretation of GW190814, suggesting the secondary object could be a hybrid star.

Contribution

It introduces a systematic study of hybrid star matter properties with the vBag model and explores implications for GW190814's secondary object.

Findings

Maximum neutron star mass with pure hadronic matter is around 2.55 solar masses.

Hadron-quark phase transition can produce hybrid stars compatible with GW190814.

Tidal deformability constraints vary depending on the phase transition model used.

Abstract

The properties of the neutron stars are calculated for the hadronic matter within the density-dependent relativistic mean-field model (DD-RMF). The phase transition to the quark matter is studied and the hybrid star matter properties are systematically calculated using the Vector-Enhanced Bag model (vBag). The maximum mass of neutron star with DD-LZ1 and DD-RMF parameter sets is found to be around 2.55$M_{\odot}$ for pure hadronic phase and around 2$M_{\odot}$ for hadron-quark mixed phase using both Gibbs and Maxwell construction. The tidal deformability for the hybrid EoS at 1.4$M_{\odot}$, $\Lambda_{1.4}$, remains unchanged from the pure hadronic EoS with Maxwell construction, but decreases with the increasing neutron star mass for Gibbs construction. While the pure hadron matter EoS satisfies the mass constraint from recently observed GW190814 data, implying a stiff neutron star EoS, the hadron-quark phase transition satisfies the constraints from the recent observations GW170817. Therefore, we cannot exclude the possibility of the secondary object in GW190814 as a neutron star with a phase transition to the quark matter that satisfies the 2$M_{\odot}$ maximum mass limit.